Blade construction and propeller blade



9, 195@ E. s. BUCE-ZER ETAL BLADE CONSTRUCTION AND PROPELLER BLADE 5 Sheecs-Sheet 1 Filed Feb. 26, 1.945

May 9, E1950 E. s. BUCHER ETAL BLADE CONSTRUCTION AND PROPELLER BLADE 5 Sheets-Sheet 2 fredfi. fill 0Z2; .79:

Filed Feb. 26, 1945 May 9 1950 E. s. BUCHER ETAL BLADE CONSTRUCTION AND PROPELLER BLADE 5 Sheets-Sheet 3 Filed Feb. 26, 1945 Elflay $3 1954) E. s. BUCHER EE'AL BLADE CONSTRUCTION AND PROPELLER BLADE 5 Sheets-$heet Filed Feb 26, 1.945

ZSmaentors zmw z 9 395$ E. s. EUQHER ETAL BLADE CONSTRUCTION AND PROPEL R BLADE 5 Sheets-5heqt 5 Filed. Feb. 26, 1945 Ismaentors EdwaM/S. fluz/zer 276625. ZZZ/027171:

Patented May 9, 1950 UNITED STATES PATENT OFFICE BLADE CONSTRUGTION AND PROPELLER BLAD Application February 26, 1945, Serial No. 579,810

This invention relates to blade constructions and propeller blades and more particularly, to a reinforced plastic propeller blade wherein the reinforcing members form a part of the airfoil blade surface.

The invention has particular reference to a propeller blade construction characterized by metal sections disposed in facing relation to pros vide major portions of the camber and thrust surfaces of the blade and wherein the leading and trailing edge areas thereof are formed of a molded non-metallic composition.

The invention has further reference to a hollow propeller blade construction characterized by a metal shank including metal sections extending longitudinally therefrom and disposed in facing relation to provide major portions of the camber and thrust surfaces including the tip portion of the blade wherein the leading and trailing edge areas thereof are formed of a molded non-metallic composition.

More specifically, the invention relates to a propeller blade wherein a cylindrical metal shank includes one or more integral spine or loadcarrying plate sections extending longitudinally of the blade and one or more plastic sections supported by the spine section or sections, said spine and plastic sections having airfoil configuration and forming the camber and thrust surfaces including the leading and trailing edge portions respectively of a complete propeller blade.

The invention has further reference to a hollow steel shell which is formed with a cylindrical shank end and a closed tip end but without leading and trailing edge airfoil portions, a plastic core filling said shell short of its shank end and forming the leading and trailing edges of a propeller blade, the steel and plastic surfaces b.8- ing flush with each other.

The invention has still further reference to a reinforced plastic propeller blade wherein the metal reinforcing spine or load-carrying member, including a cylindrical shank portion, is formed of two duplicate half sections, having substantially convex configuration and disposed in facing relation and welded or otherwise secured together to form a unitary, tapered, hollow load-carrying structure, said structure having propeller blade pitch imparted thereto before the plastic blade portion or portions are bonded thereto.

The invention has further reference to a hollow metallic blade-forming spine having convex major surfaces and substantially parallel, oppo:

2 C a ms no m sitely disposed leading and trailing edge forming fins or plates attached intermediate the side f ce th o aid n a n b ed r e arge a inal g s. wh r y t d fin a ecess on each side of said fins and between said side faces and sai enlar ed. m i l e e f r he reception of a molded plastic whose outer surfaces blend with said convex surfaces and form an uninterrupted blade surface having airfoil cone figuration.

Various other objects, advantages and features of the invention will become apparent from the following detailed description,

The invention resides in the blade construction, propeller blade, combinations and bonding features of the character hereinafter described and claimed.

For an understanding of the invention and for an illustration of several forms thereof, reference is to be had to the accompanying drawings, in which:

Figure 1 is a plan view of a propeller bladeforming plate as struck out from a blank indicated by the broken lines;

Fig. 2 is a longitudinal sectional view taken on the line 2-2 of Fig. 1, the broken lines illustrating the rib-forming stock which is added to the integral plate rib Figs. 3, 4 and 5 are transverse sectional views taken on the respective lines 3-3, l-4 and 5-5 of Fig. 1;

Fig. 6 is a plan view of a blade-forming plate after convexity has been formed therein, the marginal edges thereof turned over and hernilind ic sei fi rati n given to the a krmins se mo Fig. 7 is a longitudinal sectional view taken on he i e' l f F the'broken line il ustratingthe built-up rib stoclswhich is removed n tap n t r b bns t d na y;

Figs. 8, 9 and 10 are transverse sectional views taken n th respec ive es 8-6. 9-9 and Ede-59 of Fig. 6;

Fig. 11 is a plan View of a blade construction constructed inaccordance with one form of the nv nt- 1 i lu trate the pe a a dg and the manner of positioning a solid blade tip hereon;

i .12 is a longitudin l ect onal view taken on the line l2-,.-l2 of Fig. 11;

Figs. 13, 1. 1 and 15 are transverse sectional views taken on the respective lines l3-|3, i i-i l and l5.-.-l5 of Fig. 11;

Fig. 16 is an edge view of a propeller blade formed from the blade construction of Fig. 11, said propeller blade having pitch therein and the leading and trailing edges being formed of plastic material;

Figs. 17, 18 and 19 are transverse sectional views taken on the respective lines I'I--I'I, I8-I8 and I9I9 of Fig. 16;

Fig. 20 is a fragmentary plan view of a modification wherein the major portion of the blade tip is formed integral with each of the plates forming the blade;

Fig. 21 is a fragmentary longitudinal sectional view taken on the line 2 I2I of Fig. 20;

Fig. 22 is a plan view of a modified form of propeller blade construction constructed in accordance with the invention, said blade construction having a solid tip secured thereto and being without twist and completed airfoil surfaces;

Fig. 23 is an edge view of a propeller blade formed from the blade construction of Fig. 22, said propeller blade having pitch and plastic sections;

Figs. 24, 25 and 26 are transverse sectional views taken on the respective lines 24-44, 2525 and 26-25 of Fig. 23;

Fig. 27 is a plan view of another propeller blade construction;

Fig. 27a is a fragmentary side-edge View of the shank portion of the blade construction shown in Fig. 27 and illustrating the manner in which the plate surfaces extend in spaced relation from the tubular shank end;

Fig. 28 is a marginal edge view of a propeller blade formed from the blade construction of Fig. 27, said propeller blade having pitch and having a plastic composition bonded thereto to complete the airfoil surfaces of the blade; and

Figs. 29, 30 and 31 are transverse sectional views taken on the respective lines 2929, 3030 and 3I-3I of Fig. 28.

Referring to the drawings and to Fig. 1 in particular, the broken lines Ill, represent the metallic plate stock from which one of two propeller blade-forming plate members P, shown in solid lines, is formed.

In accordance with the invention, the blank plate In is first milled or forge rolled throughout its length to uniformly reduce the original thickness thereof as indicated at I2, Figs. 2 and 3. Subsequently, the plate stock, so reduced in thickness, is subjected to a further milling operation wherein a plurality of milling cutters, differing in diameter and suitably spaced on a milling machine arbor, further reduce the thickness of the plate uniformly along its longitudinal center line from a point adjacent one end thereof as indicated at A, to its opposite end B. In this operation, one milling cutter forms a shallow channel I3 and the cutters spaced from the central cutter on either side thereof, being of greater diameter, reduce the marginal plate portions I4 to approximately half the thickness of the central plate portion whereby a pair of spaced parallel ribs I5, extending lengthwise of the plate, are formed and the central channel portion I3 together with the marginal edge portions I4 reduced to the desired dissimilar thickness as clearly shown in Figs. 1 through 5.

The ribs I resulting from the aforesaid milling operation, while of insufiicient height for a subsequent taper milling operation, are formed primarily to provide surfaces more readily adapted for welding additional rib-forming stock thereon short of one end of each rib l5, as indicated by the broken lines I5a in Figs. 2, 4, 5, 6

4 and '7. It will be apparent that if the ribs I5 were not formed on the plate Ill, metallic stock adapted for rib-forming purposes, would have to be separately welded thereon and unnecessarily involve problems of location, alinement, etc., as will be understood. Accordingly, each of the ribs I 5 is built-up with additional metallic stock, preferably although not necessarily, by welding a supplemental section of plate stock I5a on the initially formed ribs I5 as clearly shown in Figs. 4, 5 and '7. After the initially formed ribs I5 have been so increased in height, the plate II] is again subjected to a further milling operation wherein the previously milled plate surfaces I3 and I4 and the supplemental rib sections Ifia, are tapered from A to B, as seen in Fig. 7, whereby the thickness of the plate I!) and the height of the rib sections I5a, including one end portion of the initial ribs I 5, are progressively reduced. The foregoing operations are the same for all plates required to form a propeller blade structure in accordance with the invention, such plates being, therefore, identical up to this point.

In the next operation, in accordance with the invention, the milled plate I0 is placed in a suitable die to blank out the plate P therefrom. During this operation, the shank-forming end portion I6, previously reduced in thickness as indicated at I2 in 3, is undercut or pierced, as at IT, Fig. 1, to separate said portion I6 from the ends of the ribs I5, where the second milling operation was terminated, to facilitate subsequent bending of the said shank-forming portion I 8 into substantially hemi-cylindrical form.

Subsequently, a pair of plates P so blanked are next formed into plates of opposite hand and without twist, two dies, right and left hand, being required for this operation as will be understood. In this latter operation, convexity is imparted to the plates, the marginal edges I8 bent over substantially at right angles and the shank portion I6 formed into hemi-cylindrical form, Figs. 6-10 inclusive.

After the plates P have been formed as aforesaid, the longitudinal edge surfaces IGa of the hemi-cylindrical shank I617 are in alinement with the tapered ribs Ifia, as shown in Fig. 6, but separated by the intervening spaces developed as a result of the previously formed slots I'I. These slots are now closed by suitably fusing a deposit of metal therein, by means of a suitable welding operation, whereby the ribs I50. and the edges defining the hemi-cylindrical shank I6b form a continuous edge surface.

After convexity has been imparted thereto as aforesaid, each plate P is again subjected to a further milling operation wherein final cuts including a bevel cut I9 are made on the upper face of the respective ribs I50, and the hemicylindrical shank I 61) as at I9. At the same time, a finish cut is also made along the turned-up face of the marginal edges I8.

Subsequently, in accordance with the invention, two plates P of opposite hand are preferably placed in a suitable jig or fixture in facing relation and welded together along the grooves formed by the respective sets of beveled edges I9 as indicated at W, Figs. 13-15 inclusive to form a propeller blade construction. After two plates P have been so welded together, the weld seam along the side of each pair of ribs is preferably milled or ground down to a uniformly smooth surface and a solid tip end 2I, having a reduced shank 22, is fitted into the box-like channel 23 formed by the tapered ribs I51; and the intermediate plate surfaces, the tip shank 22 being subsequently welded in place whereby the blade construction so formed is provided with the completely shaped tip closing the outer end of the longitudinal channel 23 extending between the plates P as clearly shown in Figs. 11 and 12.

With the blade construction thus far completed, a spine or load-carrying member is produced which is initially without twist, and with the external surfaces thereof disposed, preferably although not necessarily, symmetrically with respect to a plane extending longitudinally thereof as indicated by the broken line L in Figs. 12 to 15 inclusive. The spine or load-carrying member of the hereinafter described modification of the invention illustrated in Figs. 22-26 inclusive, while not so illustrated, is also symmetrical before blade twist is imparted, thereto,

Thus, the blade construction has its external surfaces disposed symmetrically, or substantially so, with respect to a plane extending longitudinally of said blade construction. In the several forms of the invention disclosed, this plane is the aforesaid plane L which coincides with the plane surfaces described. The blade construction is symmetrical by reason of the fact that any line extending perpendicular to the plane L and in tersecting one side of said blade construction has the same length, between the plane L and the point of intersection, as the length of a straight-line extension of said line between said plane L and the point of intersection thereof with the opposite side of the blade construction.

While it is an important feature of the present invention that the external surfaces of the spine or load-carrying members, herein shown and described, be symmetrical with respect to a plane extending longitudinally thereof, as above described, the invention is not to be limited thereto since similar structures or members having non-symmetrical external surfaces may also be utilized in accordance therewith.

Thereafter, pitch or twist is next imparted to the symmetrical spine or load-carrying member by means of a blow-up die of the character shown in Patent 2,350,541 before the leading and trailing plastic edge areas are molded or otherwise formed thereon. In this operation, the temperature of the blade construction is elevated to a suitable degree and immediately placed in the blow-up die whereupon gas or air under suitable pressure is admitted into the interior thereof whereby said blade construction is caused to partake of the configuration of the blow-up die.

After the above noted pitch-imparting operation, the longitudinal cavities 24 on each side of the blade construction, Figs. 18 and 19, are filled with a suitable plastic compound whereupon the blade construction is placed in a molding die, appropriate for the purpose, and subjected to heat and pressure whereby the plastic compound is polymerized and molded to form the leading and trailing edge areas 25 and 25, Figs. l6, l8 and 19, these being flush with the outer surface of each of the plates P and securely anchored and bonded therebetween. Moreover, in the said molding operation, the exterior surfaces of the adhering plastic sections are given airfoil configuration and also propeller blade pitch formation as will be understood. As clearly shown in Figs. 16 through 19, it will be readily apparent that the leading and trailing edge areas 25 and 26 respectively, of the completed propeller blade, are formed by the plastic material molded within the longitudinal cavities 24 in interlocked relation with the marginal plate portions ll of the plates P and the inwardly bent marginal edges I8 thereof whereby the molded material is firmly held in intimate relation therewith as will be understood. It will be observed that the respective plastic edge areas 25 and 26 extend from the weld juncture between the blade tip 2| and the channel 23 to points adjacent the shank 21, Fig. 16, where the said molded plastic portions terminate flush with the cylindrical shank surface.

In such propeller blade applications where blade cuffs are desirable, the plastic edge areas .25 and 25 .are extended in the manner indicated by the broken lines 28 in Fig. 11 to form cuffs or fairings 29 as an integral part of the respective leading and trailing plastic edges.

Figs. 20 and 21 illustrate a modified form of the invention wherein the attached tip 2 I, previously described, is dispensed with, and the plates P formed initially to include a blade tip defining portion at with the tip portion 36 of one plate out slightly shorter than the tip portion of the other plate. Thus, when two plates are brought together in facing relation, the tip end of one plate will extend beyond the shortened tip end of the other plate to provide a weld clearance whereby a desirable weld W may be effected between the respective tip defining ends as clearly shown in Fig. 21. In this form of the invention, the plastic leading and trailing edge areas 25 and 28 extend substantially out to the blade tip forming portions 36 to complete the contour thereof as clearly shown by the broken lines in Fig. 20.

In a further modification of the invention, as shown in Figs. 22 to 26 inclusive, the spine or load-carrying member or structure 3| is produced from two plane, longitudinally tapered plate members which are each die-formed to provide a hemi-cylindrical end portion 32 and a channel like portion 33 extending longitudinally therefrom, the side walls of said channel portion 33 diminishing in height as the end thereof is approached. The two plates PI so formed are of opposite hand and they are welded together in facing relation to form the hollow spine member indicated at 3!. Thereafter, thespine member 35 has suitable fins or plates 34 bonded or other wise secured thereto, each of these being .provided with an enlarged marginal edge bead 35o adapted to form a, metallic propeller blade edge. Thereafter, a complete blade tip section Bl, having a reduced shank end, is fitted into the outer end of the hollow spine member 3i and suitably welded thereto tocomplete the spine structure. Thereupon, said spine structure is subjected to a pitch-imparting operation wherein the spine structure is first elevated to a suitable temperature and immediately placed in a blow-up die, adapted for this particular modification, to impart all of the pitch of a complete propeller blade thereto preparatory to molding a plastic composition thereon to form complete airfoil surfaces.

The blow-up die utilized in the operation of imparting pitch to the spine member 33 is so designed and constructed that while air or gas under suitable pressure imparts pitch to the hollow central portion of the spine 3 I, the fins or plates 34, associated therewith, are given a corresponding pitch at the same time by complementary die surfaces which come into direct contact with the fins or plates 34 throughout their length as will be understood.

Thereafter, the intervening spaces between the enlarged marginal edges of the fins 34 and the hollow spine member 3| on both sides of said fins 34, are filled with a suitable plastic composition and subsequently placed in an appropriate molding die and subjected to heat and pressure whereby the plastic composition is polymerized and bonded to the adjacent metallic surfaces in intimate relation therewith. The airfoil blade surfaces thus completed including the exterior surfaces of the adhering plastic sections have airfoil configuration and also propeller blade pitch formation as clearly shown in Figs. 25 and 25.

In another modification of the invention illustrated in Figs. 27 to 31 inclusive, a pair of plane tapered plate members, without ribs and leading and trailing edge-forming areas, are utilized to form a cylindrical shank section and a pair of spaced spine or load-carrying members extending longitudinally therefrom in converging relation to form a solid tip at the opposite ends of said plate members in a manner generally similar to that described in connection with Fig. 21.

In this modified form of the invention, each of the plate members, produced as a result of a taper milling operation and a blanking operation, as previously described in connection with Fig. l, is subjected to a die-forming operation whereby there is produced a plate P2 having a hemicylindrical shank-forming portion 38 from which extends a plate section 38a having convexity and pitch formation.

Thereafter, two of such plate members P2 substantially of opposite hand are disposed in facing relation and joined together, by means of a welding operation, along the abutting faces of the hemi-cylindrical sections 38, to form a cylindrical shank end 33. At the tip, one plate member is slightly shorter than the other plate member in order to provide clearance whereby to more readily efiect a desirable weld between the blade tips as indicated at W2.

As a result of the aforesaid welding operations, an open shell of substantially propeller blade configuration devoid of leading and trailing edgeforming areas but having all of the pitch of a completed propeller blade is produced, the said pitch formation being subsequently checked for warpage, resulting from a welding operation, by placing a suitable sectional mandrel within the blade shell and, if necessary, working the outer surfaces thereof in various known manners to correct for such warpage as may be present. Thereafter, the metallic blade shell is brought to final propeller blade configuration by molding a plastic composition to and between the joined plate members forming the shell, in an appropriate die, by means of heat and pressure whereby a plastic core 40 including leading and trailing edge areas 4| and 42 are formed thereon flush with the outer surface of the metallic shell, and with all of the pitch formation and airfoil configuration of a complete propeller blade as clearly shown in Figs. 28, 30 and 31. It will be noted that the plastic leading and trailing edge areas 4! and 42 extend from the blade tip to a location adjacent the shank end where they blend into the outer cylindrical surface thereof, as at 43, and short of the root end, interiorly thereof as indicated at 44.

In all of the modifications shown and described,

the plastic sections of the blade may be extended and so molded as to provid a cuff or fairing, as indicated by the broken lines 28 in Fig. 11, whereby the pitch formation and airfoil configuration is carried further along the blade short of its root end and the attachment of separate cuff-forming sections dispensed with.

Whil the invention has been described with respect to certain preferred examples which give satisfactory results, it will be understood by those skilled in the art after understanding the invention, that various changes and modifications may be made without departing from the spirit and scope thereof and it is intended therefore in the appended claims to cover all such changes and modifications.

What is claimed as new and desired to be seecured by Letters Patent, is:

l. A propeller blade comprising a hollow substantially rectangular metal box girder of which two of the opposed outside faces form parts of the blade exterior surface, plastic filler bonded to and extending from the other two opposed faces of said girder and forming parts of the leading and trailing dges of said blade, and metal reinforcing elements, extending chordwise of the blade substantially from the central parts of said other opposed faces of the girder, to which said filler is also bonded, one of said elements extending through said filler to form a metallic exposed edge strip at said leading edge.

2. A propeller blade comprising a hollow substantially rectangular metal box girder of which two of the opposed outside faces form parts of the blade exterior surface, plastic filler bonded to and extending from the other two opposed faces of said girder and forming at least parts of the leading and trailing edges of said blade, and metal reinforcing elements, extending chordwise of the blade from said other opposed faces of the girder, to which said filler is also bonded, said reinforcing elements lying substantially in the neutral plane of the blade profile and being embraced by said plastic filler, and the reinforcing element on the leading edge side of said girder extending through said filler and forming a metallic leading edge strip on said blade.

EDWARD S. BUCHER. FRED B. ELLIOTT, JR.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,996,850 Bendix Apr. 9, 1935 2,323,165 Thomas June 29, 1943 2,350,541 Stulen et al June 6, 1944 2,370,136 Berliner Feb. 2'7, 1945 2,383,342 Riley Aug. 21, 1945 2,386,527 Wiberg Oct. 9, 1945 FOREIGN PATENTS Number Country Date 334,127 Italy 1936 439,407 Great Britain Dec. 5, 1935 459,472 France Sept. 6, 1913 

